The invention relates to a process for the production of a face-to-face carpet fabric on a double pile loom having at least two filling insertion planes, using filling yarns, stuffer warp yarns, and chain warp yarns to form the back cloths in the form of a bottom cloth and a top cloth, as well as frames of pile yarns per warp course to form the patterned pile layer between the two back cloths, whose respectively non-patterning pile yarns are tied into the back cloths of the top and/or bottom cloths largely under tension and whose respectively patterning pile yarns are stretched alternately between the filling yarns of the top cloth and the bottom cloth; whereby the filling yarns within a pattern repeat in both back cloths are inserted in at least two different filling insertion planes, at least once as a back filling outside the stuffer warp and at least once as an inner filling inside the stuffer warp; whereby in each back cloth, groups of chain warp yarns are fed according to a prescribed pattern repeat, forming weaving sheds, whereby the chain warp yarns of a group staggered within a pattern repeat in the warp direction, loop in harmonizing weaving sequences outside the back fillings and inner fillings with respect to a back cloth, whereby each chain warp yarn of a groupxe2x80x94within a weaving sequencexe2x80x94between its respective last binding to an inner filling and the subsequent last binding to a back filling is guided over several filling insertion cycles behind the inner fillings, forming a holding length, and then inside an inner filling in a compensating length, forming a weaving shed, and whereby the pattern repeats of the chain warp yarns are designed so that the tie-in length of the chain warp yarns of a group within each pattern repeat is compensated for between them.
A process of this type is known from EP 628 649 A1. It shows, for example, the customary state of the art up to now. The chain warps are arranged regularly in groups of two chain warp yarns. Each group is assigned respectively to a warp course. Each warp course has respectively such a group of chain warp yarns, at least one stuffer warp yarn, and a frame of pile yarns.
A group of chain warp yarns is characterized in that it holds within its pattern repeat all the back fillings and all the inner fillings in its effective area on the stuffer warp, which is tied in under tension, and optionally on the dead piles, which are tied in under tension.
It is customary thereby to guide the individual chain warp yarns of a group within a pattern repeat of a specific weaving sequence by means of shafts during the formation of the weaving shed. Because only a single warp beam is available as a rule for the chain warp yarns on a double pile loom, the chain warp yarns have been woven in regularly according to a uniform weaving sequence, so that the tie-in length and thus the tension of all chain warp yarns of a group can be held constant within a pattern repeat.
Those skilled in the art regularly focus on not exceeding a certain pattern repeat size and a certain temporary difference in consumption in order to ensure that the tension of the chain warp yarns running from a single warp beam is uniform. In practice, a so-called two-course rib weave (cf. Hans Osswald, xe2x80x9cDie Teppichindustriexe2x80x9d 1965, Melliand Textilberichte, Heidelberg, p. 112, FIGS. 176 and 177) was used regularly on face-to-face carpet looms for the two-shuttle production of the backing. In this two-shuttle three-shot weave with a pattern repeat of six filling insertion cycles, in one of the two back cloths a chain warp yarn regularly extended diagonally from one inner filling to a back filling inserted four courses later and from there back again to an inner filling in the two immediately succeeding courses.
With this type of tie-in, the intermediate pile binding point was drawn very tightly to the previously formed back cloth by means of the diagonal section, let us call it the xe2x80x9cholding lengthxe2x80x9d, of the chain warp yarn. The shorter section guided through the back cloth, which we call the xe2x80x9ccompensating length,xe2x80x9d then fixed the position of the chain warp yarn in the back cloth, so that when the chain warp yarn tension slackened in the shed area, the finished fabric could not loosen again.
Such a weave already ensures that the quality of the tie-in of the pile legs will be serviceable. There are specific limits to the filling density, however.
The asymmetrically tied-in chain warp causes the fillings carrying and supporting the pile loops to be deflected in the warp direction along the stuffer warp or along the dead piles. The exit direction of the pile loops regularly deviates by up to 10xc2x0 and more from the vertical to the back cloth. Such an inclined position of the pile legs is regularly the reason that certain required resilience properties can only be ensured by increasing the pile density and/or by raising the pile height. Both measures for ensuring the desired resilience properties require a considerable additional expense for pile material. The costs for a carpet produced in this manner are correspondingly high.
A further disadvantage of this asymmetrical weave of the back cloth is that the recovery power of the pile cover under partial severe loadingxe2x80x94for example by the feet of pieces of furniturexe2x80x94is insufficient.
Intensive brushing processes and the like may be required to remove partial pressure points. Usually, however, such pressure points leave permanent and clearly visible deformations in the pile surface.
Due to the inclined position of the pile legs, carpets woven in this manner cannot be lined up next to one another for contract use. The differing reflection angles of the incident light, which are caused as a function of the respective weave direction, give an observer the impression that there are color defects.
In order to limit the inclination of the pile angles, attempts have already been made (cf. Osswald, p. 112) to increase the thickness of the back cloth by inserting intermediate fillings that separate the stuffer warp from the dead pile strand. It was also hoped that this would enable the deflection of the fillings on the back cloth to be reduced.
This measure, with a specific arrangement of the fillings inserted successively or simultaneously in the area of a pattern repeat, had only limited success as far as the orientation of the pile legs was concerned (cf. DE 574 920).
There was a distinct increase in the quantity of material used. The pile density was not increased further by these measures.
In EP 628 649 A1 referred to initially, a solution to this problem was attempted in that other filling yarn arrangements were used, while keeping the intermediate filling. The chain warp yarns were guided over the filling yarns in such a way that they loaded the filling yarns approximately symmetrically in the warp direction. The filling yarnsxe2x80x94inserted as back filling, intermediate filling, or inner fillingxe2x80x94are this held largely immobile in the warp direction. The size of the pattern repeat was maintained in the customary manner with four filling insertion cycles. This led to an increased yarn material requirement for chain warp yarns. The pile density, measured in the warp direction, also remained clearly limited in this case. Carpets produced in this manner frequently had to be placed in lower quality categories due to inadequate density.
For the said reasons, the production of very dense pile goods was normally previously reserved for the single-shuttle weaving technique, in which not every pile loop is tied to a back filling. Much lower productivity was accepted.
EP 922 799 A2 shows an attempt to increase pile density even using a two-shuttle method. In each back cloth. the top cloth and the bottom cloth, the pile loops in a warp course are stretched alternately on a back filling and then on an intermediate fillingxe2x80x94which is inserted between the stuffer warp and the dead piles. The pattern repeat of the chain warp yarns extends over eight courses. The initially defined holding length is formed in each weaving direction in three successive courses.
The goods achievable using intermediate fillings and back fillings as pile carrying fillings are of lower quality. The appearance of the back of the carpet differs considerably from the appearance of the pile side. The pile loops at the borders of the pattern, which are only bound via an intermediate filling, have a distinctly lower pull-out resistance. During the usual care with a vacuum cleaner, these pile loops are gradually detached from their weave and removed. The final result of this is unclear pattern contours. A higher pile density is only achieved to a limited extent.
In Belgian Patent 675 494, an attempt was made to achieve a greater pile density even when all the pile loops are stretched over a back filling, using a similar basic weave of the chain warp. Here, the dead piles were guided under tension on the back of the bottom cloth and after the weaving procedure and the separation of the face-to-face carpet fabric, were scratched off from the back of the bottom cloth in the pile plane. These so-called xe2x80x9cscratch-off goodsxe2x80x9d are known to be of unsatisfactory quality.
It is an object of the present invention to provide a process for fixing the back cloths with dead piles distributed in the top cloth and bottom cloth and tied in by means of chain warp yarns, which process on the one hand ensures a largely vertical tie-in of the pile legs in the back cloths, enables a carpet fabric to be produced with a high pile density, and ensures that the quantity of material used in the area of the back cloths can be distinctly reduced.
It is furthermore an object of the invention to ensure, by means of the measures found, that the resilience properties of the carpet are the same or better, the quantity of pile material used being reduced.
This objective is accomplished by a process in accordance with which the combination of the designated process steps prevents back fillings from being deflected in the warp direction relative to the inner fillings. It prevents the points of intersection of two chain warp yarns of two groups always being positioned in one and the same transversal area of the back cloth in adjacent warp courses during the shed treadle motion.
Surprisingly, the combination enables the pile density in the warp direction to be increased by up to 30%, depending on the weave variant selected and the thickness of the filling yarns used.
The pile loops project regularly from the back cloth largely vertically and are stable and securely supported in this position. This leads to excellent resilience properties in the finished carpets.
The recovery power of the pile surface after partial severe loading is optimized.
The varying reflectance of the colors as a function of weave direction is distinctly reduced. The use of pile carpet for contract carpeting is no longer generally excluded.
Depending on the weave selected in the scope of the invention, chain warp material can be saved in orders of magnitude of between 10 and 25%.
A saving of pile material results from the fact that a lower pile height can be selected to achieve the same resilience properties, due to the vertical pile tie-in.
In addition to said advantages, another embodiment has the additional advantage that the pile binding points on the carpet back are distributed uniformly and free of lines, especially when 4 chain warp yarns are used per group. The carpet back resembles the classical hand-knotted carpet and has the additional advantages of the taut stuffer warp.
In contrast to known basic weaves, the pile density was able to be increased with a relatively small pattern repeat by up to 15 pile rows/dm, and in variants with a substantially larger pattern repeat by up to more than 100 pile rows/dm.
Depending on the length of the pattern repeat, the modification according to a further embodiment enables a distinct saving (up to over 25%) of chain warp material while maintaining the classical back appearance of a carpetxe2x80x94analogous to the conventional 2/2 rib weave. Here too it is possible to increase the pile density considerably.
In accordance with an advantageous embodiment of the invention, a group of the chain warp yarns is suitably distributed over 3 to 4 warp courses. Again there is a high pile density and a distinct saving of chain warp material.
The advantages of the weave according to a further embodiment are that in addition to an attractive saving of chain warp material, improved pile position, and improved pile density, high wear resistance can be ensured, even in the unbound state.
In accordance with another embodiment, a variant is defined that is important in particular for working with three overlapping filling insertion planes. The most essential advantages are a high saving of chain warp material while maintaining high wear resistance of the carpet.
Yet a further advantageous embodiment describes a second basic method to achieve the object of the invention in a limited area of the pattern repeat, which has the same results as those described in relation to the initial embodiment described above.
A still further embodiment of the invention is directed to an almost equivalent method to the first embodiment described herein. The pile loops do not tie over a back filling in every case. The pattern of the front face of the carpet is not reproduced completely on the back, however. This weave is desirable where the demands on the quality of the carpet are not particularly high and the price is to be kept correspondingly low.
The invention is explained in greater detail below by means of examples with reference to the accompanying drawings.